A high-performance long-wave infrared photodetector based on a WSe₂/PdSe₂ broken-gap heterodiode

Layered narrow bandgap quasi-two-dimensional (2D) transition metal dichalcogenides (TMDs) demonstrated excellent performance in long-wave infrared (LWIR) detection. However, the low light on/off ratio and specific detectivity (D*) due to the high dark current of the device fabricated using a single narrow bandgap material hindered its wide application. Herein, we report a type-III broken-gap band-alignment WSe₂/PdSe₂ van der Waals (vdW) heterostructure. The heterodiode device has a prominently low dark current and exhibits a high photoresponsivity (R) of 55.3 A W^-1 and a high light on/off ratio >10⁵ in the visible range. Notably, the WSe₂/PdSe₂ heterodiode shows an excellent uncooled LWIR response, with an R of ∼0.3 A W^-1, a low noise equivalence power (NEP) of 4.5 × 10^-11 W Hz^-1/2, and a high D* of 1.8 × 10⁸ cm Hz^1/2 W^-1. This work provides a new approach for designing high-performance room-temperature operational LWIR photodetectors.